As a bright yellow color, crocin/crocetin has been in use for over a thousand years. Usually the colorants are extracted from dried saffron stigma or from the dried fruits of gardenia.
Saffron is obtained by drying the stigmas from the flower of Crocus sativus L., whose cultivation probably began during prehistoric Greek times. About 200 stigmas are required to obtain 1 g of colorant. The basic components of saffron, which are responsible for its strong yellow-red color, are cis- and trans-crocins, a family of water-soluble carotenoids.
Saffron (Crocus sativus) is not a vegetable, although in some areas of the world the corms of various crocus species are eaten by local peasants. Saffron is one of the most expensive spices on the earth, which has a pleasant spicy, pungent, bitter taste and a tenacious odor. Fortunately, small quantities of saffron go a long way in terms of flavoring. Besides being steeped in tea, it is used for seasoning many foods such as fancy rolls, biscuits, rice, and fish. The slender dried flower stigmas of the saffron constitute the true saffron of commerce. Both of the wholesale price and the retail price are expensive in the marketplace, but saffron has always been popular as a yellowish orange natural dyestuff.
Gardenia (Gardenia jasminoides) is another prevailing plant being used for yellow dye. Gardenia has also been used in Japan and China as herbal drugs for their antiphlogistic, diuretic, antipyretic, haemostatic, and cholagogic effects, and can be used to treat contusions. A paste of the herb with flour and wine is used as a poultice on twists, sprains, strains, bruises, and abscesses; very effective in injuries to tendons, ligaments, joints and muscles. Furthermore, it is an important crude drug in traditional Asian medical prescriptions, which have sedative, antipyretic, diuretic, choleretic, and anti-inflammatory effects. Gardenia yellow has been listed in The Japanese Pharmacopoeia as crude drug. In Chinese medicine, it is considered to have anti-inflammatory, antipyretic, astringent, and haemostatic functions as well as use in the treatment of mastitis. It is also used for irritation, sore and swollen eyes and abscesses.
Gardenia yellow is a yellowish food colorant and a member of the carotenoid family. Its principal pigments are crocin/crocetin derivatives. Gardenia yellow is obtained by extraction with water or ethanol from the fruit of Gardenia. The main component of gardenia yellow is crocin, which is now generally used as a natural yellow pigment. It is very soluble in water compared to other carotenoids. Gardenia yellow is listed in the list of existing food additives in Japan. For example, gardenia yellow pigment has been used as food colorant for Japanese traditional foods, such as ohan (yellow rice colored with gardenia fruit) and kuri-kanroni (yellow chestnuts colored with gardenia fruit and soaked in syrup).
Crocetin is a natural carotenoid dicarboxylic acid (8,8′-Diapo-ψ,ψ-carotenedioic acid), which is a brick red crystal with a melting point of 285° C. Chemically, crocetin is a polyene di-carboxylic acid (8,8′-diapocarotene-8,8′-diolic acid), whose central unit consists of seven conjugated double bonds and four chain methyl groups. When one or both of the end-groups (carboxyl groups) of crocetin are esterified with glucose or gentiobiose, di-esters of crocetin are produced which can have two equal or different end-groups.
In one aspect, crocin is bis(6-O-β-D-glucopyranosyl-β-D-glucopyranosyl)ester, α-crocin, or di-gentiobiose ester of crocetin, having a chemical structure as shown below:

In a broader sense, crocin also includes natural carotenoids where the sugar moiety is not limited to digentiobiose, and can be defined as a diester formed as the condensation product of any saccharide and the dicarboxylic acid crocetin. This is shown below:
wherein R is any sugar residue and each R, independently, can be the same or different.
The chemical structure of crocetin is shown as below,
which is the central core of crocin, and is also the compound responsible for the color of saffron. Crocetin is commercially obtained by hydrolyzing crocin to remove digentiobiose of crocin.
Crocin has been shown to be a potent antioxidant, as well as being useful for anti-depression, cancer prevention, enhancing mental function, lowering high cholesterol, and/or inflammation prevention. Crocin, crocetin and its derivatives have also been shown to be able to stimulate bile secretion significantly, being useful to improve many conditions. In China, a saffron multi-glycoside tablet has been approved as a novel oral drug for the treatment of coronary heart disease and angina. This drug product consists of a series of components extracted from saffron, among which crocin is established as the main effective ingredient and the standard control.
Crocin is a unique water-soluble carotenoid, which has attracted much research attention for its extensive pharmacological effects. Current research provides that crocin has a big molecular structure that is unsuitable to be absorbed in vivo. It was also found that crocin was not absorbed after oral administration to animals and healthy volunteers (Phytomedicine 14 (2007) 633-36).
Crocetin is recognized as one of the active metabolites of crocin in the body, but the increase of crocetin was not significant after repeated oral dose, which indicates that crocetin was rapidly eliminated without accumulation in the body. One possible reason might be that crocetin is insoluble in water. Low solubility in water limits many practical applications in food, beverage, drug or nutraceuticals, which also result in reduced bioavailability in vivo.
The investigations on the biological and pharmacological activities of crocin/crocetin were obtained from the experiments in vitro or on animals, but few studies have taken into account the bioavailability of crocin/crocetin and their derivatives.
Therefore, a need exits for suitable crocin/crocetin derivatives that have increased bioavailability relative to crocin or crocetin.